The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1887-12-31


tinent it enters in between headlands like
the capes mentioned, and the wave is COM
pressed from each end; and the volume of
water that is travelling in being but little
reduced, it must of necessity rise higher as
it becomes compressed. There are bays
and inlets where the tidal wave is COM
pressed very rapidly. st. John is on such
a-bay. At the head of the bay of Fundy
the volume of water runs in unreduced,
but much compressed, until the food tide
reaches the enormous height of fifty feet,
when the sun and the moon pull together
the best they are able. The rise of the
tide under such circumstances is very rapid
the friction of the land serving to hold the
water back. Veracious travellers who have
been to the Bay of Fundy say that the
hogs of the natives feed luxuriously on the
CLAIMS in the bay that are exposed at low
water, and yet never get fat because they
have to run so furiously to save their lives
when once the water starts in that they
use up all the fat that the clans eaten
would have made.
The correspondents reference to the
tidal wave entering Long Island Sound
and the Narrows at one instant suggests
another cause for variation in the heights
and durations of tides. The tidal wave
enters the Sound at Block Island at about
the time that it enters the lower bay at
Sandy Hook (not the Narrows), sometimes
two minutes quicker, sometimes six min
utes later. One wave sweeps up the Sound
and the other through the Narrows, the
upper bay, East River and He'll Gate.
One has a fairly unobstructed course, and
the other tortuous one. They meet at
various points between Astoria and Throg's
Neck. 1t is said that if dam could be
built across He'll Gate where the tall cleo
trio light tower stands the water on one
side of the dam would sometimes be five
feet higher than on the other. This would
be due to the fact that one high tide had
got there long before the other. Some
times one would be ahead, and again the
other. We do not know why this is so.
The friction of the water on the beds Of
the channels partly, but not wholly, explains
the phenomenon. 1t is partly because of
this friction that the second tidal wave of
the day was retarded twenty three minutes
at Sandy Hook and thirty-four minutes at
Hell Gate on certain day, but that does
not wholly explain it. The officers of the
Coast Survey are keeping accurate records
of the tides wherever they are at work If
the appropriations hold out they will prob
ably know all about the matter in few
years, but many millions of observations
| will have to be taken and considered first.
There is, Of course, tidal wave in the
seas below the Cape of Good Hope as vol
as elsewhere in the ocean, but this great
Southern wave sweeps into the South
Atlantic unobstructed, while the heavenly
bodies have to get up, as one may say,
new wave in the Atlantic after passing
over the Eastern continent. This new
wave and that portion of the Southern sea
wave from around the point of Africa,
which is DETECTED upon the coast of South
America, interfere with each other. Very
likely the wave from the South modifies
the tide at New York 1t certainly modi-
fies the tide at Galveston, Texas. Calves
ton has only one tide day instead of two.
1t is said that one tidal wave sweeps into
the Gulf of Mexico around the point of
Yucatan, and another around the point of
Florida The two reach Galveston az
different hours, so that one neutralizes the
other entirely at one hour for high tide and
nearly so at the next, the only rise of the
day being due to the fact that the intervals
of the two waves are not the same.
One very interesting and in some places
dangerous tidal phenomenon is called the
bore. Owing to the shape and position of
some estuaries the tidal wave comes in as a
huge, foam capped breaker that travels
with mighty roar and carries destruction
to all frail objects that happen to be in its
path The bore is seen in its greatest
glory perhaps in the Amazon River. On
account of the course and shape and length
of this estuary it. happens that as many as
eight high tides may be travelling up the
stream at once, of which five may be roar
ing bores These bores are from II to Is
feet high.
There is a difference between tidal
wave and a tidal current, although most
people confound the two. The current is
due to the wave, of course, but the tide
may be rising in a place when no current
is visible. That is, the surface of the
water may be rising while there is no per-
ceptible current running in. In fact, the
water in New York harbor is often rising
when the surface current is running out,
and vice versa. This is due to rndercur-
rents. The water on the surface ruEs one
way, while below it a more powerful cur
rent is running the other In the Chesa-
peakc Bay the crest of the high water wave
travels up the bay at the rate of fifteen
miles an hour, while the current is nowhere
more than one mile an hour. The tidal
wave enters this bay smoothly and quietly,
but why it should do so there when it
makes such terrible fuss running up the
Amazon is not fully understood. The diff
ference in the form of the shores does not
explain it. There is great volume Of
water pouring out Of the Amazon, while
but little pours out of the Chesapeake.
This may partly explain the difference, be-
cause ordinary rollers always break in the
mouth of river when the current out is
strong.
While the heaping up of the water is due
to the attraction of the moon and sun, the
water at any point is not highest when
those bodies pass the plane of the places
meridian. High water comes along good
deal later, as rule The interval varies
with the time in the month, but not, as a
rule, very much. This interval is called
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